^Looking east down Illinois 138 from Illinois 4 in Benld, April 2020.
Illinois Route 138 connects a few communities that grew due to the mining industry, located north of St. Louis. It runs east-west for about ten miles in southern Macoupin County.
The western end of Illinois 138 is at Illinois 159 near Bunker Hill, where it starts to head eastward toward Interstate 55:
At Mount Clare, Illinois 138 joins Illinois 4 south for a short distance:
In Benld (pronounced "Ben-ulled"), a town with a ridiculous combination of consonants, Illinois 138 splits off of Illinois 4 to continue east:
Illinois 138 has an interchange with Interstate 55 approaching Mount Olive, but Illinois 138 isn't quite done yet:
Illinois 138 ends in the town of Mount Olive, not at any currently-signed highway, but at a former alignment of US Route 66...